1. Field of the Invention
The present invention relates to a laser module for optical communication.
2. Related Background of the Invention
A fiber grating laser is described in the following literature, which discloses the related art in this field: “Technical Report of IEICE, EMD2002-24, CPM2002-66, OPE2002-46, LQE2002-101 (2002-08), The Institute of Electronics, Information and Communication Engineers.” This fiber grating laser does not include a peltier element and is therefore a non-temperature controlled type device. The fiber grating laser exhibits temperature dependency of a wavelength and electric-current dependency thereof which are superior to those of a distributed feedback (DFB) semiconductor laser. An oscillation wavelength of the fiber grating laser is defined by a correlation between a longitudinal mode of an external optical cavity, which is constituted by a semiconductor optical amplifier device and a fiber grating, and a reflection characteristic-of the fiber grating. As shown in FIG. 2 of the literature, the fiber grating laser is configured to include at least one longitudinal-mode line within a reflection bandwidth of the fiber grating. Moreover, as shown in FIG. 4 of the literature, the fiber grating laser is small in size.